Influence of the Fe2+ ion triple clusters on the magnetic susceptibility of Fe-based diluted magnetic semiconductors
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Low lying energy levels of Fe2+ ion triples in the cubic-structure iron-based diluted magnetic semiconductors are calculated on the basis of a model which includes crystal field, spin-orbit interaction, Zeeman interaction and Heisenberg-type exchange interaction. Using this energy level diagram the magnetic susceptibility of a crystal is calculated in the nearest-neighbour (NN) and in the extended NN pair approximation, We find that the Fe2+ ion triples contribute to the temperature dependent susceptibility up to the lowest temperatures investigated, T greater than or equal to 1 K. It appears that the triple Fe2+ ion clusters may explain at least a part of the low-temperature increase of the magnetic susceptibility which is observed in these magnetic materials. (C) 2001 Elsevier Science B.V. All rights reserved.